Papers by Keyword: Liquid Infiltration

Abstract: High volume fraction SiC/Al composite material, with its excellent thermal properties and flexible preparation process, has been widely used in the field of electronic packaging. In the paprer, the development of SiC/Al materials for electronic packaging and their preparation methods are reviewed. The preparation processes for preparing SiC/Al by liquid infiltration are mainly introduced. The advantages and disadvantages of several important processes are analyzed. Finally, the development trend of SiC/Al for electronic packaging prepared by liquid infiltration is prospected.

Abstract: In this work, one stage and two stages compaction technique were used to fabricate the tungsten-copper composite powder. Liquid infiltration technique was used to consolidate the W-Cu green compact and a low concentration iron powder was added as activation material to enhance the sintering behavior. In addition, two-steps compaction process was developed for improving mechanical properties of W-Cu composite as well as segregation of Fe around W grain. The green compact was directly infiltrated at 1250 °C for about 2 hours under vacuum conditions. The microstructure, inter-boundary layer and the contamination levels of the infiltrated compacts were characterized using the scanning electron microscope (SEM) and the energy dispersive X-ray analysis (EDX). Relative sintering density varied in the range of 97.1 to 99.3 % of theoretical density, and it was highly depended on Fe concentration and method of compaction. In contrast to one stage compaction, the experimental results showed that the composites fabricated by the two stages of compact ion had better homogeneous structure, high densification and a clear segregation of inter-boundary layer of Fe-W around W grains.

Abstract: Extrusion directly following vacuum infiltration is a special forming technique that combines the advantages of liquid metal infiltration and semisolid extrusion. The major advantages of this process are elimination of porosity and shrinkage, good surface finish, good dimensional accuracy, high strength to weight ratio and near net shaping. Magnesium matrix composites are fabricated usually through stirring casting, powder forming, injecting deposition, liquid metal infiltration or die casting at present time. However few investigations on magnesium matrix composite are conducted for the specific characteristics of magnesium alloy, such as high chemical activity and easy oxidation. The present paper is focused on Csf/Mg composites obtained via infiltration of porous short carbon fiber preform by liquid Magnesium. The complete experiment setup is designed and fabricated by ourselves, which include the forming molds, the unit for melting the magnesium, the unit for vacuuming and the monitoring and collecting system of forming process parameters. In this method the whole experiment setup is vacuumed firstly. Then the pressurized nitrogen is used to infiltrate the magnesium melt through a porous preform of short carbon fibers. After the infiltration completed, the punch of the press extrude the magnesium-infiltrated preform out of the forming die to form the tubes or bars. X-ray diffraction (XRD), optical and SEM microscopes were used to characterize the infiltration and the microstructure of fabricated composites. The compression test was used to characterize the mechanical properties of fabricated composites. The results show that the preform was infiltrated thoroughly by melt magnesium and the fabricated Csf/Mg composites have excellent mechanical properties compared with the magnesium alloys. Csf/Mg composites should be very promising candidates for automobile parts and portable electronic appliance parts in the future.

Abstract: Many process parameters are involved during the fabrication of Csf/Mg composites using extrusion directly following vacuum infiltration. The selection of suitable process parameters is important for the successful fabrication of composites. This will require a continuous monitoring and collecting system of process parameters. This paper describes how this is performed. The monitoring and collecting system is developed to monitor and control the forming process successfully. The hardware was built with data acquisition (DAQ) card based on PCI and various sensors for temperature, pressure, displacement. The industrial computer is used to process the data collected from the sensors. The data acquisition card is the bridge between the computer and sensors. In order to reduce the signal noise from sensors, the hardware filter circuit is designed. The data acquisition card can not work by connecting the computer and sensors through it simply. It must be operated through the self-developed software. The data colletcing software is developed in this paper. It can realize the parameter monitoring and collecting easily by setting up the hardware through the user friendly interface. The curves of parameters can be displayed on the computer screen and the data can be saved into the database for post-processing. The software also supplies the warning function. When the parameters (for example the temperature of mold) arrives the set value, the computer can sound a note of warning to tell the worker to operate the press. It is demonstrated that the main parameters, such as temperature of mold and liquid metal, the loaded pressure and the displacement of punch, can be monitored and collected in real-time by use of this system. This paper found the base for the further selection of optimized process parameters.